“Boost your immune system” is a familiar fall message. Of course, it’s beneficial to strengthen your body’s ability to fight off germs at this time of year, but this is just one piece of the puzzle.
The immune system is a dynamic, adaptive system that learns and responds throughout the year and over time. In addition to a seasonal reset, you can train your immune system every day with high-quality sleep, proper nutrition, stress management, adequate movement, and supplementation.
These daily habits can shape how resilient you are heading into cold and flu season.
Immune resilience
Considering immune overactivity involved in allergic diseases, autoimmunity, and chronic inflammation, modern immunology is exploring the concept of immune resilience.
Immune resilience refers to the ability of the immune system to respond to a threat (such as a virus) in a regulated manner and then quickly promote recovery by restoring pre-exposure levels of inflammation and immunocompetence (disease resistance).
Age, exercise, psychosocial stress, gut microbiota, and chronic inflammation can all impact immune resilience.
Immune adaptability
A resilient immune system depends on effective communication between the innate and adaptive immune systems.
The innate immune system is the body’s first line of defence against intruders. It responds quickly and non-specifically against a threat, such as bacteria in a cut. But if the innate system can’t neutralize the threat, it calls in the adaptive system.
The adaptive immune system then mounts specific responses against pathogens. It remembers past infections so that it may respond more accurately and quickly with successive infections.
Exposome
Growing evidence suggests that our lifestyle and environmental exposures, collectively referred to as the “exposome,” exert a measurable effect on immune health.
These exposures may include the following:
- pollution
- smoking
- circadian rhythm and sleep
- physical activity
- diet
- gut microbiome
- stress
- sunlight
Circadian rhythm
Our sleep-wake cycle isn’t the only thing regulated by our 24-hour circadian rhythm.
Melatonin, a hormone released at night to make us sleep, is also an immunomodulator that exerts anti-inflammatory effects. Circadian regulation also drives immune cell recirculation through lymphoid organs.
However, a variety of factors can disrupt circadian rhythm:
Disruption of the circadian rhythm contributes to a loss of rhythmicity in immune cell production, a dysregulation of the inflammatory response, increased autoimmunity, and a greater susceptibility to infections.
Circadian Rx
Morning sunlight exposure is the strongest environmental cue for circadian regulation. Aim for at least 30 minutes of sunlight exposure before 10 am.
Impose a screen-free rule 30 to 60 minutes before you’d like to be asleep.
Sleep
High-quality sleep is associated with improved immunity and enhanced immune memory.
Sleep Rx
Aim for seven to nine hours of high-quality sleep per night by getting regular exercise, maintaining a consistent sleep/wake cycle (even on weekends!), following a relaxing bedtime routine, and adopting a contemplative practice such as meditation.
Try to avoid disruptors that are associated with poor-quality sleep:
- caffeine
- alcohol
- heavy meals
- light exposure later in the day
Movement
A high level of cardiorespiratory fitness (CRF) is associated with fewer days of illness from acute respiratory infections compared to a low level of CRF.
Regular exercise can also mitigate immunosenescence, the immune dysfunction that naturally occurs as we age and increases susceptibility to infections. Physically active older adults have less immunosenescence compared with their sedentary counterparts.
Movement Rx
The minimum international recommendation is at least 150 minutes of moderate to vigorous aerobic activity per week.
For older adults and those with chronic diseases, aim for regular bouts of short-lasting (less than 45 minutes), moderate intensity exercise to enhance immune defences.
7 unexpected habits that make you harder to infect
- Spend time outdoors to reduce systemic inflammation and improve innate immunity.
- Take a brief walk in cold weather to modulate immune responses.
- Get dirty in the garden to diversify microbial exposure, which contributes to immune modulation.
- Hum or sing daily to stimulate the sinuses’ production of nitric oxide, which has antimicrobial and antiviral properties.
- Use a humidifier set between 40 and 60% to avoid dry indoor air, which enhances viral transmission.
- Prioritize social connection, which is associated with increased antiviral immunity.
- Use a sauna to enhance respiratory health and reduce the risk of respiratory conditions.
Food
The nutrients involved in the growth of immune cells include the following:
- vitamins C and D
- minerals zinc and iron
- amino acid glutamine
Zinc; iron; copper; selenium; and vitamins A, D, B6, and B12 also play a role in the immune response to viral infections.
The Mediterranean diet is rich in these immune-supportive nutrients and offers antioxidant, anti-inflammatory, and immunomodulatory effects. It has been shown to be protective against predictors of morbidity and mortality in patients with COVID-19.
Food Rx
Embrace a diet rich in vegetables and fruits (vitamins C, A), fish (vitamins D, B6, B12, glutamine), lean meats (protein), legumes (iron), and nuts and seeds (selenium, zinc, copper).
Avoid ultra-processed foods with a high content of fat, sugar, salt, and additives. These substances can increase inflammation and impair immune function.
Gut microbiome
The gut microbiome assists in the training and development of major components of the innate and adaptive immune systems. It also plays an important role in immune tolerance, inflammation, and protection against bacterial pathogens and viral respiratory infections.
Physical exercise, psychosocial stress, tobacco and alcohol use, and diet can impact the composition and function of the gut microbiome.
Gut Rx
A Cochrane systematic review demonstrated that probiotic supplementation significantly reduced episodes of acute upper respiratory tract infections and antibiotic usage in both children and adults.
Stress
Psychological stress can trigger immune dysfunction, may contribute to low-grade chronic inflammation, and is associated with a higher risk of acute respiratory infections in a dose-response manner .
Stress Rx
Mindfulness-based stress reduction induces significant decreases in markers of low-grade chronic inflammation. Try meditation, relaxation techniques, or yoga to modulate the immune response.
Sunlight
The influenza virus is rapidly inactivated when exposed to ultraviolet radiation from sunlight. Low levels of ultraviolet radiation are moderately associated with higher transmissibility of SARS-CoV-2, the virus that causes COVID-19.
The vitamin D we produce from exposure to sunlight modulates both the adaptive and innate branches of the immune system and regulates the expression of genes that code for antimicrobial proteins in immune cells.
Sunlight Rx
Aim for five to 30 minutes of sunlight exposure on bare skin per day.
A resilient immune system is built, not boosted. By supporting the factors that shape immune function every day, you can help prepare your body for whatever the cold, flu, and virus season brings.
Resilience support
| Supplement | Benefit for cold, flu, and virus prevention |
| vitamin D3 | status is inversely correlated with risk and severity of acute respiratory tract infection |
| vitamin C | exerts anti-inflammatory, immune-enhancing, and pathogen-clearing effects against infectious disease |
| zinc | exerts antiviral activity against the common cold |
| echinacea | has antiviral activity against respiratory pathogens |
| beta carotene | higher dietary carotenoid intake is inversely associated with acute respiratory infection risk |
| probiotics | may reduce the incidence, duration, and severity of respiratory tract infections |
| oil of oregano | has antimicrobial and anti-inflammatory effects |
| reishi | may exert immunomodulatory effects |
| elderberry | may reduce duration and severity of the common cold |
| lysine | may reduce recurrence, severity, and duration of herpes simplex virus infections |
| polyphenols | may have antiviral activity, which has shown promise in the prophylaxis and treatment of COVID-19 |
| garlic | has antimicrobial compounds |
Mini stressors that actually enhance immunity
Hormesis is an adaptive response to mild stress that improves functionality and tolerance to more severe challenges.
This concept applies to the immune system, in that both the innate and adaptive arms can be trained to respond with greater flexibility and resilience against future stressors.
Hormetic stressors such as exercise, fasting, cold water immersion, and heat exposure (such as a sauna) can improve inflammatory control and stress adaptation.
This article was originally published in the September 2026 issue of alive magazine.
